Por"phy*ry (?), n.; pl.
Porphyries (#). [F. porphyre, L.
porphyrites, fr. Gr. ? like purple, fr. ? purple. See
Purple.] (Geol.) A term used somewhat loosely to
designate a rock consisting of a fine-grained base (usually
feldspathic) through which crystals, as of feldspar or quartz, are
disseminated. There are red, purple, and green varieties, which are
highly esteemed as marbles.
Porphyry shell (Zoöl.), a
handsome marine gastropod shell (Oliva porphyria), having a
dark red or brown polished surface, marked with light spots, like
porphyry.